1. Field of the Invention
This invention relates broadly to surgical implants. More particularly, this invention relates to a bone fracture fixation system.
2. State of the Art
Fracture to the metaphyseal portion of a long bone can be difficult to treat. Improper treatment can result in deformity and long-term discomfort.
By way of example, a Colles' fracture is a fracture resulting from compressive forces being placed on the distal radius, and which causes backward or dorsal displacement of the distal fragment and radial deviation of the hand at the wrist. Often, a Colles' fracture will result in multiple bone fragments which are movable and out of alignment relative to each other. If not properly treated, such fractures may result in permanent wrist deformity and limited articulation of the wrist. It is therefore important to align the fracture and fixate the bones relative to each other so that proper healing may occur.
Alignment and fixation of a metaphyseal fracture (occurring at the extremity of a shaft of a long bone) are typically performed by one of several methods: casting, external fixation, pinning, and plating. Casting is non-invasive, but may not be able to maintain alignment of the fracture where many bone fragments exist. Therefore, as an alternative, external fixators may be used. External fixators utilize a method known as ligamentotaxis, which provides distraction forces across the joint and permits the fracture to be aligned based upon the tension placed on the surrounding ligaments. However, while external fixators can maintain the position of the wrist bones, it may nevertheless be difficult in certain fractures to first provide the bones in proper alignment. In addition, external fixators are often not suitable for fractures resulting in multiple bone fragments. Pinning with K-wires (Kirschner wires) is an invasive procedure whereby pins are positioned into the various fragments. This is a difficult and time consuming procedure that provides limited fixation if the bone is comminuted or osteoporotic. Plating utilizes a stabilizing metal plate typically placed against the dorsal side of a bone, and screws extending from the plate into holes drilled in the bone fragments to provide stabilized fixation of the fragments.
In some cases, a relatively proximal diaphyseal portion as well as the distal metaphyseal portion of the radius may be fractured. In these cases, fragment plates are often used in conjunction with the distal radius plate. There is a disadvantage, however, in using two plates rather than one. It results in unsupported bone between the two implants. The resultant load supported by the bone between the plates in a concentrated manner. Thus, it would be desirable to provide an integrated implant which shares the load across the entire implant for distal and mid-shaft fractures.
U.S. Pat. No. 5,190,544 to Chapman et al. describes a modular plating system including a metaphyseal plate and a diaphyseal plate which are interconnected via a dovetail slot and then secured to the bone with cortical bone screws to lock the plates together. The integrity of such a system is subject to loosening in the event the bone screws loosen their engagement with the bone, e.g., through micromotion. Furthermore, if the bone is of poor quality, e.g., as a result of multiple fractures along the bone portion underlying the components, integrity between the components may never be accomplished. In addition, the metaphyseal component which receives an end of the diaphyseal fragment plate is significantly thicker (approximately 75% percent thicker) and wider (approximately 35% wider) than the fragment plate, providing an undesirably thick metaphyseal plate and creating a potentially irritating transition in two dimensions from the metaphyseal plate to the diaphyseal plate where the metaphyseal plate ends.